Pharmaceutical and Non-Pharmaceutical Interventions

To better understand the protective effects of prior infection and repeated vaccination against SARS-CoV-2 during periods of Omicron predominance, Nicole Ngai Yung Tsang from the University of Hong Kong led a prospective cohort study involving a representative community of 10,000 individuals across multiple Omicron variant waves from 2022 to 2024. The study demonstrated that repeated vaccination offered significant protection against infection with the BA.2 and BA.4/BA.5 strains. Furthermore, Tsang and colleagues found that recent prior infection provided the strongest protection against reinfection with the BA.2, BA.4/BA.5, BA.2.75, and XBB variants.

As part of ongoing efforts to evaluate and strengthen public vaccination strategies, two representatives from the Vaccine Effectiveness, Burden and Impact Studies (VEBIS) for COVID-19 and Influenza presented new findings from recent European vaccination campaigns. Esther Kissling, from Epiconcept, reported an overall 44% protection rate during the 2024–25 autumn COVID-19 vaccine campaign. Notably, vaccine effectiveness was highest in the first two months following vaccination, reaching 60%, but this protection declined to 30% during the subsequent two months, resulting in an average effectiveness of 44% over the four-month period. Meanwhile, Heloïse Lucaccioni, also from Epiconcept, highlighted that influenza vaccination prevented nearly two-thirds of medically attended influenza cases among children in primary care during the 2024–25 season in Europe. Furthermore, no major variations of protection were observed between age groups within the pediatric age.

Additionally, research from the CSL group provided valuable insights into improving Influenza A vaccines. Alicia Stein, of CSL Seqirus Australia, assessed the relative effectiveness of cell-based versus egg-based influenza vaccines in a cohort of over 100,000 individuals during the 2023–24 season in the United States. The findings indicated that cell-based vaccines offered superior effectiveness in both paediatric and adult populations compared with egg-based formulations. Moreover, Frank R. Albano, also from CSL Seqirus Australia, presented data from two-phase randomised controlled trials investigating new high-dose formulations of cell-derived influenza vaccines adjuvanted with MF59, in adults over 50 years of age. The trials showed that formulations containing both an intermediate dose of MF59 and a higher dose of HA antigens elicited the strongest immune responses without raising safety concerns. This formulation has now been selected for further validation in a Phase 3 study.

In conclusion, the session shed light on the evolving landscape of vaccination for SARS-CoV-2 and Influenza A worldwide, offering new perspectives on maximising vaccine effectiveness through improved formulations and strategic implementation. These findings underscore the importance of continued research and adaptability in optimising protection against these pervasive respiratory viruses.